0001664710-21-000018 | 10-K | XBRL Viewer

Cover - USD ($) $ in Millions	12 Months Ended
Cover - USD ($) $ in Millions	Dec. 31, 2020	Mar. 19, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39264
Entity Registrant Name	KEROS THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-1173868
Entity Address, Address Line One	99 Hayden Avenue,
Entity Address, Address Line Two	Suite 120, Building E
Entity Address, City or Town	Lexington,
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02421
City Area Code	617
Local Phone Number	314-6297
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	KROS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 386.0
Entity Common Stock, Shares Outstanding		23,270,717
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s proxy statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A in connection with the registrant’s 2021 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such proxy statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the registrant’s fiscal year ended December 31, 2020.
Entity Central Index Key	0001664710
Amendment Flag	false
Document Fiscal Year Period	FY
Document Fiscal Year Focus	2020

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
CURRENT ASSETS:
Cash and cash equivalents	$ 265,876	$ 7,020
Prepaid expenses and other current assets	1,850	381
Deferred initial public offering costs	0	604
Research and development incentive receivable	0	922
Total current assets	267,726	8,927
Operating lease right-of-use assets	878	1,205
Property and equipment, net	724	708
Restricted cash	115	115
TOTAL ASSETS	269,443	10,955
CURRENT LIABILITIES:
Accounts payable	2,149	2,088
Current portion of operating lease liabilities	423	376
Accrued expenses and other current liabilities	4,612	2,022
Total current liabilities	7,184	4,486
Operating lease liabilities, net of current portion	476	899
Preferred stock tranche liability	0	4,956
Other liabilities	62	119
Total liabilities	7,722	10,460
COMMITMENTS AND CONTINGENCIES (Note 13)
Convertible preferred stock, carrying amount		19,941
STOCKHOLDERS’ EQUITY (DEFICIT):
Common stock, par value of $0.0001 per share; 200,000,000 and 27,000,000 shares authorized as of December 31, 2020 and December 31, 2019, respectively; 23,192,866 and 2,429,705 shares issued and outstanding as of December 31, 2020 and December 31, 2019, respectively	2	1
Additional paid-in capital	326,730	203
Accumulated deficit	(65,011)	(19,650)
Total stockholders’ equity (deficit)	261,721	(19,446)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT)	269,443	10,955
Series A Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	0	9,891
Series A1 Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	0	944
Series B1 Preferred Stock
CURRENT LIABILITIES:
Convertible preferred stock, carrying amount	$ 0	$ 9,106

Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Shares authorized (in shares)		17,289,895
Preferred stock, shares issued (in shares)		6,555,307
Preferred stock, shares outstanding (in shares)		6,555,307
Liquidation value		$ 26,038,000
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	27,000,000
Common stock, shares issued (in shares)	23,192,866	2,429,705
Common stock, shares outstanding (in shares)	23,192,866	2,429,705
Series A Preferred Stock
Par value (in USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	0	10,000,000
Preferred stock, shares issued (in shares)	0	4,607,652
Preferred stock, shares outstanding (in shares)	0	4,607,652
Liquidation value	$ 0	$ 12,271,000
Series A1 Preferred Stock
Par value (in USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	0	800,000
Preferred stock, shares issued (in shares)	0	368,612
Preferred stock, shares outstanding (in shares)	0	368,612
Liquidation value	$ 0	$ 1,171,000
Series B1 Preferred Stock
Par value (in USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	0	3,427,004
Preferred stock, shares issued (in shares)	0	1,579,043
Preferred stock, shares outstanding (in shares)	0	1,579,043
Liquidation value	$ 0	$ 12,596,000

Consolidated Statements of Operations - USD ($)	12 Months Ended
Consolidated Statements of Operations - USD ($)	Dec. 31, 2020	Dec. 31, 2019
REVENUE:
Research collaboration revenue	$ 0	$ 10,000,000
OPERATING EXPENSES:
Research and development	(33,860,000)	(17,379,000)
General and administrative	(12,797,000)	(3,184,000)
Total operating expenses	(46,657,000)	(20,563,000)
LOSS FROM OPERATIONS	(46,657,000)	(10,563,000)
OTHER INCOME (EXPENSE), NET:
Interest expense, net	(6,000)	(8,000)
Research and development incentive income	2,460,000	558,000
Change in fair value of preferred stock tranche obligation	(1,490,000)	(2,564,000)
Other income (expense), net	160,000	241,000
Total other income (expense), net	1,124,000	(1,773,000)
Loss before income taxes	(45,533,000)	(12,336,000)
Income tax benefit	172,000	0
Net loss	(45,361,000)	(12,336,000)
Net loss attributable to common stockholders—basic and diluted (Note 12)	$ (45,361,000)	$ (14,136,000)
Net loss per share attributable to common stockholders - basic and diluted (in USD per share)	$ (2.93)	$ (6.08)
Weighted-average common stock outstanding - basic and diluted (in shares)	15,506,397	2,326,857

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	IPO	Public Offering	Common Stock	Common Stock IPO	Common Stock Public Offering	ADDITIONAL PAID-IN CAPITAL	ADDITIONAL PAID-IN CAPITAL IPO	ADDITIONAL PAID-IN CAPITAL Public Offering	ACCUMULATED DEFICIT	Series A Preferred Stock	Series A1 Preferred Stock	Series B1 Preferred Stock	Series C preferred stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Ending balance (in shares)				2,243,648
Ending balance	$ (7,183)			$ 1			$ 130			$ (7,314)
Beginning balance (in shares) at Dec. 31, 2018											4,607,652	368,612	1,579,043	0
Beginning balance at Dec. 31, 2018											$ 9,891	$ 944	$ 9,106	$ 0
Ending balance (in shares) at Dec. 31, 2019	6,555,307										4,607,652	368,612	1,579,043	0
Ending balance at Dec. 31, 2019	$ 19,941										$ 9,891	$ 944	$ 9,106	$ 0
Beginning balance (in shares) at Dec. 31, 2018				2,243,648
Beginning balance at Dec. 31, 2018	(7,183)			$ 1			130			(7,314)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)				82,387
Exercise of common stock options	14						14
Vesting of restricted stock (in shares)				103,670
Vesting of restricted stock	0
Stock-based compensation	59						59
Net loss	(12,336)									(12,336)
Ending balance (in shares)				2,243,648
Ending balance	(7,183)			$ 1			130			(7,314)
Ending balance (in shares)				2,429,705
Ending balance	(19,446)			$ 1			203			(19,650)
Issuance of series C convertible preferred stock, net of issuance costs of $227 (in shares)														4,169,822
Issuance of Series C convertible preferred stock, net of issuance costs of $227	(8)						(8)							$ 55,781
Conversion of convertible preferred stock upon initial public offering (in shares)				10,725,129							(4,607,652)	(368,612)	(1,579,043)	(4,169,822)
Conversion of convertible preferred stock upon initial public offering	75,722			$ 1			75,721				$ (9,891)	$ (944)	$ (9,106)	$ (55,781)
Ending balance (in shares) at Dec. 31, 2020											0	0	0	0
Ending balance at Dec. 31, 2020											$ 0	$ 0	$ 0	$ 0
Beginning balance (in shares) at Dec. 31, 2019				2,429,705
Beginning balance at Dec. 31, 2019	(19,446)			$ 1			203			(19,650)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Series C convertible preferred stock, net of issuance costs of $227	(8)						(8)							$ 55,781
Settlement of preferred stock tranche liability	6,446						6,446
Conversion of convertible preferred stock upon initial public offering (in shares)				10,725,129							(4,607,652)	(368,612)	(1,579,043)	(4,169,822)
Conversion of convertible preferred stock upon initial public offering	$ 75,722			$ 1			75,721				$ (9,891)	$ (944)	$ (9,106)	$ (55,781)
Issuance of common stock, net of underwriting discounts, commissions and offering costs (in shares)					6,900,000	2,990,000
Issuance of common stock, net of underwriting discounts, commissions and offering costs		$ 100,123	$ 140,110					$ 100,123	$ 140,110
Exercise of common stock options (in shares)	113,475			113,475
Exercise of common stock options	$ 38						38
Vesting of restricted stock (in shares)				34,557
Vesting of restricted stock	0
Stock-based compensation	4,097						4,097
Net loss	(45,361)									(45,361)
Ending balance (in shares)				2,429,705
Ending balance	(19,446)			$ 1			203			(19,650)
Ending balance (in shares)				23,192,866
Ending balance	$ 261,721			$ 2			$ 326,730			$ (65,011)

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares
Common stock, par value (in USD per share)	$ 0.0001
Stock issuance costs \| $	$ 8,970
Underwriting discounts, commissions and offering costs \| $	$ 9,390
Series A Preferred Stock
Par value (in USD per share)	$ 0.0001
Series A1 Preferred Stock
Par value (in USD per share)	0.0001
Series B1 Preferred Stock
Par value (in USD per share)	0.0001
Series C preferred stock
Par value (in USD per share)	$ 0.0001
Stock issuance costs \| $	$ 227

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (45,361)	$ (12,336)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	278	208
Stock-based compensation expense	4,097	59
Non-cash lease expense	327	230
Changes in fair value of preferred stock tranche obligation	1,490	2,565
Changes in operating assets and liabilities:
Research and development incentive receivable	922	(552)
Prepaid expenses and other current assets	(1,469)	1,891
Deferred IPO costs	604	(300)
Accounts payable	61	1,312
Operating lease liabilities	(376)	(213)
Deferred revenue	0	(10,000)
Accrued expenses and other current liabilities	2,590	1,191
Other liabilities	(57)	(53)
Net cash used in operating activities	(36,894)	(15,998)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(294)	(271)
Net cash used in investing activities	(294)	(271)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of Series C preferred stock	56,000	0
Payment of Series C preferred stock issuance costs	(227)	0
Proceeds from issuance of common stock, from the initial public offering, net of underwriting discounts of $7,728	102,672	0
Payment of initial public offering costs	(2,549)	0
Proceeds from issuance of common stock, from follow-on financing, net of underwriting discounts of $8,970	140,530	0
Payment of follow-on financing offering costs	(420)	0
Proceeds from exercise of stock options	38	14
Net cash provided by financing activities	296,044	14
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	258,856	(16,255)
Cash, cash equivalents and restricted cash at beginning of year	7,135	23,390
Cash, cash equivalents and restricted cash at end of year	265,991	7,135
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for taxes	0	256
Settlement of preferred stock tranche obligation	6,446	0
Right-of-use assets obtained in exchange for operating lease obligation	44	700
Deferred IPO costs in accounts payable and accrued expenses	0	304
Conversion of preferred stock into common stock upon closing of initial public offering	75,714	0
Reconciliation of cash, cash equivalents and restricted cash
Total cash, cash equivalents and restricted cash	$ 265,991	$ 23,390

Consolidated Statements of Cash Flows (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Statement of Cash Flows [Abstract]
Underwriting discounts, initial public offering	$ 7,728
Underwriting discounts, public offering	$ 8,970

Nature of Business and Basis of Presentation	12 Months Ended
Nature of Business and Basis of Presentation	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	NATURE OF BUSINESS AND BASIS OF PRESENTATION Keros Therapeutics, Inc. (“Keros” or the “Company”) was incorporated in 2015 as a Delaware corporation. Its principal offices are in Lexington, Massachusetts. The Company is a clinical stage company dedicated to the discovery and development of breakthrough therapeutics for neuromuscular diseases. The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries, Keros Therapeutics Australia Pty Ltd (“Keros Australia”) and Keros Security Corporation, a Massachusetts securities corporation. Since its inception in 2015, the Company has devoted the majority of its resources to business planning, research and development of its product candidates, including conducting clinical trials and preclinical studies, raising capital and recruiting management and technical staff to support these operations. To date, the Company has not generated any revenue from product sales as none of its product candidates have been approved for commercialization. On April 13, 2020, the Company completed an initial public offering (“IPO”) in which the Company issued and sold 6,900,000 shares of its common stock, which includes 900,000 shares issued and sold pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $16.00 per share, for aggregate gross proceeds of $110.4 million. The Company received approximately $100.1 million in net proceeds after deducting underwriting discounts and commissions and offering costs. In connection with the IPO, the Company's board of directors (the "Board") and stockholders approved an amended and restated certificate of incorporation to, among other things, effect a one-for-2.1703 reverse stock split of its issued and outstanding shares of common stock and convertible preferred stock, as well as to effect a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock. The reverse stock split was effected on March 31, 2020. Accordingly, all share and per share amounts of common stock for all periods presented in the accompanying audited consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect this reverse stock split and adjustment of preferred stock conversion ratios. Upon the closing of the IPO, all of the then-outstanding shares of convertible preferred stock automatically converted into 10,725,129 shares of common stock at the applicable conversion ratio then in effect. Subsequent to the closing of the IPO, there were no shares of convertible preferred stock outstanding. On November 17, 2020, the Company completed an underwritten public offering in which the Company issued and sold 2,990,000 shares of common stock at a public offering price of $50.00 per share, which includes 390,000 shares of common stock issued pursuant to the exercise in full of the over-allotment option by the underwriters. The aggregate gross proceeds to the Company from the public offering were approximately $149.5 million. The Company received approximately $140.1 million in net proceeds after deducting underwriting discounts and commissions and offering costs. The Company’s consolidated financial statements have been prepared on the basis of the Company continuing as a going concern for the next 12 months. Management believes that the Company’s existing cash and cash equivalents, will allow the Company to continue its operations for at least the next 12 months. In the absence of a significant source of recurring revenue, the continued viability of the Company beyond that point is dependent on its ability to continue to raise additional capital to finance its operations. If the Company is unable to obtain additional funding, the Company may be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or the Company may be unable to continue operations. The accompanying consolidated financial statements have been prepared by the Company in conformity with U.S. GAAP. COVID -19 Considerations The impact of the COVID-19 pandemic on the financial performance of the Company will depend on future developments, including the continued duration and spread of the outbreak and related governmental advisories and restrictions. These developments and the impact of COVID-19 on the financial markets and the overall economy are highly uncertain and cannot be predicted. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be materially adversely affected. The Company is currently unable to determine the extent of the impact of the pandemic to its operations and financial condition.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

Principles of Consolidation

The accompanying consolidated financial statements include the accounts of the Company, Keros Australia and Keros Security Corporation. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue, and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. This process may result in actual results differing materially from those estimated amounts used in the preparation of the financial statements if these results differ from historical experience, or other assumptions do not turn out to be substantially accurate, even if such assumptions are reasonable when made. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, useful lives assigned to property and equipment, the fair values of common and preferred stock and the fair value of the preferred stock tranche obligation. The Company assesses estimates on an ongoing basis; however, actual results could materially differ from those estimates.

Fair Value Measurements

Certain assets and liabilities are reported on a recurring basis at fair value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

Level 1—Quoted prices in active markets for identical assets or liabilities.

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

An entity may choose to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected will be reported in earnings. The Company had no financial instruments measured at level 3 as of December 31, 2020.

Cash, Cash Equivalents, and Restricted Cash

Cash and cash equivalents consist of standard checking accounts and money market funds. The Company considers all highly liquid investments with an original maturity of 90 days or less at the date of purchase to be cash equivalents.

The Company’s cash equivalents, which are funds held in a money market account, are measured at fair value on a recurring basis. The carrying amount of cash equivalents was $262.0 million and $5.0 million as of December 31, 2020 and 2019, respectively, which approximates fair value and was determined based upon Level 1 inputs. The money market account is valued using quoted market prices with no valuation adjustments applied and is categorized as Level 1.

The Company had restricted cash of $0.1 million in the form of a certificate of deposit related to its operating leases in Lexington, Massachusetts as of December 31, 2020 and 2019.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity (deficit) as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations. Upon closing the IPO in April 2020, deferred offering costs were reclassified to additional paid-in capital, representing a reduction in IPO proceeds. As of December 31, 2020 and 2019, the Company had deferred offering costs of $0 and $0.6 million, respectively.

Concentrations of Credit Risk

Financial instruments that potentially subject us to significant concentration of credit risk consist primarily of cash and cash equivalents. The Company may maintain deposits in financial institutions in excess of government insured limits. The Company believes that it is not exposed to significant credit risk as its deposits are held at financial institutions that management believes to be of high credit quality and the Company has not experienced any losses on these deposits. As of December 31, 2020 and 2019, the Company’s cash and cash equivalents were held with three financial institutions. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated based on the fact that many of these securities are either government-backed or of high credit rating.

Property and Equipment

Property and equipment are recorded at cost. Expenditures for repairs and maintenance are expensed as incurred. When assets are retired or disposed of, the assets and related accumulated depreciation are derecognized from the accounts, and any resulting gain or loss is included in the determination of net loss. Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

The Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. To date, no impairments have been recognized for these assets.

Leases

The Company accounts for its leases under Accounting Standards Codification (“ASC”) Topic 842, Leases (“ASC 842”). At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than 12 months are recognized on the balance sheet as ROU assets and current and non-current lease liabilities, as applicable. The Company has elected not to recognize on the balance sheet leases with terms of 12 months or less. The Company typically only includes an initial lease term in its assessment of a lease arrangement. Options to renew a lease are not included in the Company’s assessment unless there is reasonable certainty that the Company will renew. The Company monitors its material leases on a quarterly basis.

Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected remaining lease term. Lease cost for operating leases is recognized on a straight-line basis over the lease term as an operating expense. Certain adjustments to the ROU asset may be required for items such as lease prepayments or incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which the

Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. In transition to ASC 842, the Company utilized the remaining lease term of its lease in determining the appropriate incremental borrowing rate.

For all asset classes of its leases, the Company has elected to account for the lease and non-lease components together for existing classes of underlying assets.

Guarantees and Indemnifications

As permitted under Delaware law, the Company indemnifies its officers, directors, consultants and employees for certain events or occurrences that happen by reason of the relationship with, or position held at, the Company. Through December 31, 2020, the Company had not experienced any losses related to these indemnification obligations, and no claims were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related liabilities have been established.

Research and Development Costs

Research and development costs are charged to expense as incurred. Research and development costs consist of expenses incurred in performing research and development activities, including salaries and benefits, materials and supplies, preclinical expenses, stock-based compensation expense, depreciation of equipment, contract services, facilities, and other outside expenses. Costs for external development activities are recognized based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its vendors. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense.

Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses and expensed as the related goods are delivered or the services are performed.

Research and Development Incentive

The Australian research and development tax incentive program provides tax offsets to eligible companies that engage in research and development activities and has two core components:

▪43.5% refundable tax offset for certain eligible research and development entities with an aggregated turnover of less than $20.0 million per annum; and

▪38.5% non-refundable tax offset for all other eligible research and development entities. Unused offset amounts may be able to be carried forward for use in future income years.

The Company is eligible to participate in an Australian research and development tax incentive program under which the Company is eligible to receive a cash refund from the Australian Taxation Office for a percentage of the research and development costs expended by the Company in Australia.

The Company’s estimate of the cash refund it expects to receive related to the Australian research and development tax incentive program is included in other assets in the accompanying consolidated balance sheet and such amounts are recorded as research and development incentive income in the statement of operations. The Company recognizes research and development incentive income when there is reasonable assurance that the income will be received, the relevant expenditure has been incurred, and the consideration can be reliably measured. The Company has recorded a research and development incentive receivable of $0.0 and $0.9 million and other income from Australian research and development incentives of $2.5 million and $0.6 million for the years ended December 31, 2020 and 2019, respectively, related to refundable research and development incentive income payments in Australia.

Revenue Recognition

To date, the Company has earned revenue solely under the license agreement with Novo Nordisk A/S, which was terminated in October 2020 (see Note 14).

The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). The Company enters into certain agreements that are within the scope of ASC 606, under which the Company licenses, may license or grants an option to license rights to certain of the Company’s product candidates and performs research and development services in connection with such arrangements. The terms of these arrangements typically include payment of one or more of the following: non-refundable, upfront fees; reimbursement of research and

development costs; development, clinical, regulatory and commercial sales milestone payments, and royalties on net sales of licensed products.

Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine the appropriate amount of revenue to be recognized for arrangements determined to be within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect consideration it is entitled to in exchange for the goods or services it transfers to the customer.

The promised goods or services in the Company’s arrangements typically consist of a license, or option to license, rights to the Company’s intellectual property or research and development services. The Company provides options to additional items in such arrangements, which are accounted for as separate contracts when the customer elects to exercise such options, unless the option provides a material right to the customer. Performance obligations are promised goods or services in a contract to transfer a distinct good or service to the customer and are considered distinct when (i) the customer can benefit from the good or service on its own or together with other readily available resources and (ii) the promised good or service is separately identifiable from other promises in the contract. In assessing whether promised goods or services are distinct, the Company considers factors such as the stage of development of the underlying intellectual property, the capabilities of the customer to develop the intellectual property on its own or whether the required expertise is readily available and whether the goods or services are integral or dependent to other goods or services in the contract.

The Company estimates the transaction price based on the amount expected to be received for transferring the promised goods or services in the contract. The consideration may include fixed consideration and variable consideration. At the inception of each arrangement that includes variable consideration, the Company evaluates the amount of potential payment and the likelihood that the payments will be received. The Company utilizes either the most likely amount method or expected value method to estimate the amount expected to be received based on which method best predicts the amount expected to be received. The amount of variable consideration that is included in the transaction price may be constrained and is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period.

The Company’s contracts often include development and regulatory milestone payments that are assessed under the most likely amount method and constrained if it is probable that a significant revenue reversal would occur. Milestone payments that are not within the Company’s control or the licensee’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of such development and clinical milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration and other research and development revenue in the period of adjustment.

For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of the Company’s collaboration or strategic alliance arrangements.

The Company allocates the transaction price based on the estimated standalone selling price. The Company must develop assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company utilizes key assumptions to determine the stand-alone selling price, which may include other comparable transactions, pricing considered in negotiating the transaction and the estimated costs. Variable consideration is allocated specifically to one or more performance obligations in a contract when the terms of the variable consideration relate to the satisfaction of the performance obligation and the resulting amounts allocated are consistent with the amounts the Company would expect to receive for the satisfaction of each performance obligation.

The consideration allocated to each performance obligation is recognized as revenue when control is transferred for the related goods or services. For performance obligations which consist of licenses and other promises, the Company

utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

The Company receives payments from its customers based on billing schedules established in each contract. Upfront payments and fees are recorded as deferred revenue upon receipt or when due until the Company performs its obligations under these arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional.

Foreign Currency Transactions

The functional currency for the Company’s wholly owned foreign subsidiary, Keros Australia, is the United States dollar. All foreign currency transaction gains and losses are recognized in the consolidated statement of operations.

Segment Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is made available for evaluation by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The CODM is the Company’s chief executive officer. The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular concentration is focused on the discovery and development of breakthrough therapeutics for hematological and musculoskeletal disorders with high unmet medical need.

Common Stock Valuation

Prior to the Company’s IPO in April 2020, due to the absence of an active market for the Company’s common stock, the Company utilized methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid (Valuation of Privately-Held Company Equity Securities Issued as Compensation) to estimate the fair value of its common stock. Prior to the IPO, the fair value of the shares of common stock underlying the stock-based awards were determined by the Board with input from management. Since there was no public market for the common stock prior to April 8, 2020, the Board had determined the fair value of the common stock at the time of grant of the stock-based award by considering a number of objective and subjective factors, including having valuations of the common stock performed by a third-party valuation specialist. Following the closing of the initial public offering, the fair value of the Company’s common stock is determined based on the quoted market price of the common stock.

Convertible Preferred Stock

The Company has classified convertible preferred stock, referred to as preferred stock, as temporary equity in the accompanying consolidated balance sheet due to terms that allow for redemption of the shares in cash upon certain change in control events that are outside of the Company’s control, including sale or transfer of control of the Company as holders of the preferred stock could cause redemption of the shares in these situations. The Company did not accrete the carrying values of the preferred stock to the redemption values since a liquidation event was not considered probable as of December 31, 2020. Subsequent adjustments of the carrying values to the ultimate redemption values will be made only when it becomes probable that such a liquidation event will occur.

On April 13, 2020, upon the closing of the Company's IPO, all outstanding shares of Preferred Stock converted into 10,725,129 shares of the Company's common stock. Additionally, effective April 13, 2020, the Company's amended and restated certificate of incorporation authorized the issuance of 10,000,000 shares of preferred stock. There were no outstanding shares of convertible preferred stock as of December 31, 2020.

Stock-Based Compensation

The Company accounts for all stock-based payment awards granted to employees and non-employees as stock-based compensation expense at fair value. The Company’s stock-based payments include stock options and grants of common stock, including common stock subject to vesting. The measurement date for employee awards is the date of grant, and stock-based compensation costs are recognized as expense over the employees’ requisite service period, which is the vesting period, on a straight-line basis. Prior to the adoption of Accounting Standards Update (“ASU”) No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU No. 2018-07”) as discussed below under “Recently Adopted Accounting Pronouncements”, the measurement date for non-employee awards was generally the date the services were completed, resulting in financial reporting period adjustments to stock-based compensation during the vesting terms for changes in the fair value of the awards. Since the adoption of ASU 2018-07, the measurement date for non-employee awards is the date of grant without changes in the fair value of the award. Stock-based compensation costs for non-employees are recognized as expense over the vesting period on a straight-line basis. Stock-based compensation expense is classified in the

accompanying consolidated statement of operations based on the function to which the related services are provided. The Company recognizes stock-based compensation expense for the portion of awards that have vested. Forfeitures are recorded as they occur.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The Company lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.

Income Taxes

The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss is equal to net loss for all periods presented.

Net Loss Per Share

Basic net loss per share and diluted net loss per share are computed using the weighted-average number of shares of common stock outstanding for the period. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of shares of the Company’s common stock and participating securities. The Company’s preferred stock contains participation rights in any dividend paid by the Company and is deemed to be a participating security. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded.

Diluted net loss per share is computed using the more dilutive of (a) the two-class method or (b) the if-converted method. The Company allocates earnings first to preferred stockholders based on dividend rights and then to common and preferred stockholders based on ownership interests. The weighted-average number of shares of common stock included in the computation of diluted net loss gives effect to all potentially dilutive common stock equivalent shares, including outstanding stock options and preferred stock.

Common stock equivalent shares are excluded from the computation of diluted net loss per share if their effect is antidilutive. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is generally the same as basic net loss per share attributable to common stockholders since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported net losses attributable to common stockholders for the years ended December 31, 2020 and 2019.

Recently Issued Accounting Pronouncements

In December 2019, the Financial Accounting Standards Board issued ASU No. 2019-12, Income Taxes-Simplifying the Accounting for Income Taxes (“ASU No. 2019-12”). ASU No. 2019-12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. The new guidance also simplifies aspects of the accounting for franchise taxes, enacted changes in tax laws or rates and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. ASU No. 2019-12 is effective for annual periods beginning after

December 15, 2020 and interim periods within those fiscal years, with early adoption permitted. Adoption of the standard requires certain changes to be made prospectively and certain others to be made retrospectively. The Company is currently assessing the impact of this standard on its financial condition and results of operations.

Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

FAIR VALUE MEASUREMENTS

The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values (in thousands):




DESCRIPTION	DECEMBER 31, 2020		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	262,043	$	262,043	$	—	$	—
Total financial assets	$	262,043	$	262,043	$	—	$	—




DESCRIPTION	DECEMBER 31, 2019		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	4,972	$	4,972	$	—	$	—
Total financial assets	$	4,972	$	4,972	$	—	$	—
Liability
Preferred stock tranche obligation	$	(4,956)	$	—	$	—	$	(4,956)
Total financial liabilities	$	(4,956)	$	—	$	—	$	(4,956)

There have been no transfers between fair value levels during the years ended December 31, 2020 and 2019. Prior to settlement, the Company’s Preferred Stock Tranche Obligation (defined below) was carried at fair value determined according to Level 3 inputs in the fair value hierarchy as described below. The carrying values of other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

Preferred Stock Tranche Obligation

The Company determined that its obligation to issue, and the Company’s investors’ obligation to purchase additional shares of convertible preferred stock at a fixed price (i.e. the issuance price) in subsequent tranches following the initial closings of the series A, series A-1, and series B-1 convertible preferred stock (respectively, the “Series A Preferred Stock,” “Series A-1 Preferred Stock,” and “Series B-1 Preferred Stock”, which are referred to collectively with the series B-2 convertible preferred stock (the “Series B-2 Preferred Stock”) and the series C convertible preferred stock (the “Series C Preferred Stock”) as the “Preferred Stock”) financings represented a freestanding financial instrument (the “Preferred Stock Tranche Obligation”). The freestanding financial instrument was classified as a liability on the

Company’s consolidated balance sheets and initially recorded at fair value, with changes in fair value for each reporting period recognized in other expense, net in the consolidated statement of operations.

The Board determined it was probable that the Series B-2 Preferred Stock milestone would be met, and the stockholders and the Board subsequently waived the milestone and the issuance of the Series B-2 Preferred Stock on March 2, 2020. Instead of issuing the Series B-2 Preferred Stock upon this waiver, the Company instead closed its convertible Series C Preferred Stock financing (“Series C financing”). The associated Preferred Stock Tranche Obligation was remeasured prior to settlement, with the associated $1.5 million increase in fair value recorded in the Company’s consolidated statement of operations as other expense, net. As the Series C financing was executed with related parties, the Company recognized the settlement of the Preferred Stock Tranche Obligation of $6.4 million as a capital contribution in additional paid-in capital in the Company’s consolidated balance sheets.

The following reflects the significant quantitative inputs used in the valuation of the Preferred Stock Tranche Obligation:



	MARCH 2, 2020			DECEMBER 31, 2019
Stand-alone Series B-1 Preferred Stock price (spot price)	$	7.28		$	7.28
Estimated future value of Series B-2 Preferred Stock	$	8.14		$	8.14
Discount rate	15.50		%	15.50		%
Time to liquidity (years)	0.00			0.16
Probability of tranche closing	100		%	80		%

The purchase price of the Preferred Stock at initial issuance, and all subsequent issuances was higher than the fair value of the Company’s common stock.

The following table sets forth a summary of changes in the fair value of the Company’s Preferred Stock Tranche Obligation for which fair value was determined by Level 3 inputs (in thousands):



	PREFERRED STOCK TRANCHE OBLIGATION
Balance as of January 1, 2019	$	2,392
Issuance	—
Change in fair value	2,564
Balance as of December 31, 2019	4,956
Change in fair value	1,490
Settlement of tranche obligation	(6,446)
Balance as of December 31, 2020	$	—

Fluctuations in the fair value of the Company’s Preferred Stock is the primary cause for the significant changes in fair value of the Preferred Stock Tranche Obligation. In 2020 and 2019, the enterprise value of the Company was determined using the Market Approach, specifically the Subject Company Transaction Method, which considers all share class rights and preferences, as of the date of the most recent financing. As part of the Company’s strategy, during 2019, the Company began considering the pursuit of longer-term liquidity options including a potential initial public offering, which caused an increase in the value of the Series B-1 Preferred Stock while reducing the value of the Preferred Stock Tranche Obligation.

Subsequently, in March 2020, the Company determined it was probable that the milestone criteria necessary to close the subsequent tranche would be met; as such, the value of the Preferred Stock Tranche Obligation increased. The Board then waived the milestone in favor of issuing the Series C Preferred Stock in March 2020 (see Note 6), and in doing so, the Preferred Stock Tranche Obligation was fully settled and reduced to $0 on the Company's consolidated balance sheet.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2020

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

PREPAID EXPENSES AND OTHER CURRENT ASSETS

Prepaid expenses and other current assets as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Prepaid service contracts	501		21
Income tax credit receivable	172		—
Prepaid sales tax	188		65
Prepaid rent	—		64
R&D payroll tax credit	44		—
Prepaid Insurance	785		16
Other	160		215
Total prepaid expenses and other current assets	$	1,850	$	381

Property and Equipment, Net

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

PROPERTY AND EQUIPMENT, NET

Property and equipment, net as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Computer equipment and software	$	35	$	35
Laboratory equipment	1,106		843
Office furniture	47		42
Leasehold improvements	257		241
Total	1,445		1,161
Less: accumulated depreciation	(721)		(453)
Property and equipment, net	$	724	$	708

Depreciation expense was $0.3 million and $0.2 million for each of the years ended December 31, 2020 and 2019, respectively.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES

Accrued expenses and other current liabilities as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Accrued external R&D costs	$	169	$	645
Accrued external manufacturing costs	2,265		282
Accrued compensation and benefits	1,510		749
Accrued tax	185		43
Accrued legal and consultants	265		34
Other	218		269
Total accrued expenses and other current liabilities	$	4,612	$	2,022

Accrued compensation and benefits consists primarily of accrued vacation and accrued bonus.

License Agreements	12 Months Ended
License Agreements	Dec. 31, 2020
Research and Development [Abstract]
License Agreements	LICENSE AGREEMENTS Massachusetts General Hospital On April 5, 2016, the Company entered into an exclusive patent license agreement with The General Hospital Corporation d/b/a Massachusetts General Hospital (“MGH”). Under the license agreement with MGH (as amended in May 2017 and February 2018, the “MGH Agreement”), the Company obtained an exclusive, worldwide license, with the right to sublicense, under certain patents and technical information of MGH, to make, have made, use, have used, sell, have sold, lease, have leased, import, have imported or otherwise transfer licensed products and processes for use in the treatment, diagnosis, palliation and prevention of diseases and disorders in humans and animals. The Company is required to use commercially reasonable efforts to develop and commercialize licensed products and processes and must achieve certain required diligence milestones. Under the terms of the MGH Agreement, the Company paid an initial license payment of $0.1 million in 2016, and reimbursed MGH approximately $0.3 million of prior patent prosecution expenses related to the licensed patents in 2017. The Company also issued MGH an aggregate of 358,674 shares of its common stock. Additionally, the Company is required to pay a low-five digit to mid-five digit annual maintenance fee prior to the first commercial sale of its first product or process, a mid-five digit annual maintenance fee after the first commercial sale of its first product or process that is creditable against royalties, certain clinical and regulatory milestone payments for the first three products or indications to achieve such milestones, which milestone payments are $8.6 million in the aggregate, and certain commercial milestone payments for the first three products or indications to achieve such milestones, which milestone payments are $18.0 million in the aggregate. The Company is also obligated to pay tiered royalties on net sales of licensed products ranging in the low-single digits to mid-single digits. The royalty rates are subject to up to a maximum 50% reduction for lack of a valid claim, in the event that it is necessary for the Company to obtain a license to any third-party intellectual property related to the licensed products, and generic competition. The obligation to pay royalties under the MGH Agreement expires on a licensed product-by-licensed product and country-by-country basis upon the later of expiry of the last valid claim of the licensed patents that cover such licensed product in such country or ten years from the first commercial sale of such product in such country. The Company is also obligated to pay a percentage of non-royalty-related payments received by it from sublicensees ranging in the low-double digits and a change of control fee equal to a low-single digit percentage of the payments received as part of any completed transaction up to a low seven-digit amount. The MGH Agreement expires upon expiry of the last remaining royalty obligation for a licensed product or process. Under the MGH Agreement, MGH may terminate the agreement upon the Company’s uncured material breach or insolvency, a challenge by the Company of the licensed patents and certain other specified breaches of the MGH Agreement. The Company may terminate the agreement for any reason upon specified prior written notice to MGH. Novo Nordisk A/S In addition, on December 14, 2017, the Company entered into a research collaboration and exclusive license agreement with Novo Nordisk A/S. Refer to Note 14, Revenue from Contracts with Customers, for more information regarding this agreement. LakePharma, Inc. On April 22, 2019, the Company entered into an exclusive license agreement with LakePharma, Inc. (“LakePharma”) whereby the Company licensed LakePharma’s intellectual property for research and development efforts for a license fee of $0.3 million, which is recorded as research and development expense in the Company’s consolidated statements of operations. The agreement will continue in perpetuity unless terminated by either party. LakePharma may terminate the agreement at any time.

Convertible Preferred Stock

12 Months Ended

Dec. 31, 2020

Temporary Equity Disclosure [Abstract]

Convertible Preferred Stock

CONVERTIBLE PREFERRED STOCK

On March 2, 2020, the Company authorized the sale and issuance of up to 9,049,783 shares of Series C Preferred Stock, par value $0.0001 per share, of which 4,169,822 shares were sold at a purchase price of $13.43 per share for gross proceeds of $56.0 million. Issuance costs were approximately $0.2 million. As part of the Company's Series C Preferred Stock issuance, 3,078,968 of the shares were issued to certain members and affiliates of members of the Board. All issued shares reflect the reverse stock split effected March 31, 2020 while the Board authorized shares reflect the original number of shares authorized pre-split.

restated certificate of incorporation authorized the issuance of 10,000,000 shares of preferred stock. There were no outstanding shares of Preferred Stock as of December 31, 2020.

As of December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data):



	DECEMBER 31, 2019
	PREFERRED STOCK AUTHORIZED	PREFERRED STOCK ISSUED AND OUTSTANDING	CARRYING VALUE		LIQUIDATION VALUE		COMMON STOCK ISSUABLE UPON CONVERSION
Series A Preferred Stock	10,000,000	4,607,652	$	9,891	$	12,271	4,607,652
Series A1 Preferred Stock	800,000	368,612	944		1,171		368,612
Series B1 Preferred Stock	3,427,004	1,579,043	9,106		12,596		1,579,043
Series B2 Preferred Stock	3,062,891	—	—		—		—
	17,289,895	6,555,307	$	19,941	$	26,038	6,555,307

The following is a summary of the rights and privileges of the preferred stockholders as of December 31, 2020 and 2019.

Conversion: Shares of Preferred Stock are convertible, at the option of the holder, at any time, into shares of common stock. The number of shares is determined by dividing the original issuance price by the conversion price. As such, the shares of Preferred Stock effectively convert on a one-for-one basis. These rights terminate in the event of a liquidation or winding up of the Company. No fractional shares will be issued.

Liquidation Preference: While the Preferred Stock is not redeemable, the shares are redeemable for cash in certain change of control events that are beyond the control of the Company. In the event of any liquidation or Deemed Liquation Event (as defined in the Company’s articles of incorporation), the Preferred Stockholders are entitled to the greater of (i) the original issue price of the Preferred Stock plus any accrued dividends not yet paid plus any other dividends declared and unpaid or ii) the amount payable had all classes of shares been converted to common stock. In the event of a Deemed Liquidation Event, if the assets of the Company available for distribution are insufficient to pay the Preferred Stockholders in the full amount to which they are entitled, the Preferred Stockholders shall share ratably in any distribution of the assets available for distribution in proportion to the number of shares of Preferred Stock that they hold. Note that in relation to the above, the holders of Series B-1/B-2 Preferred Stock are entitled to be paid out prior to the holders of common stock, Series A Preferred Stock and Series A-1 Preferred Stock.

Dividends: Dividends accrue at a rate of $0.17, $0.21, $0.582630 and $0.651888 per share, per year on the anniversary of the issuance date for Series A Preferred Stock, Series A-1 Preferred Stock, Series B-1 Preferred Stock and Series B-2 Preferred Stock, respectively. Dividends are cumulative; however, accrued dividends will be payable only if and when declared by the Board. Dividends on other classes of the Company’s stock may not be declared or paid unless the Preferred Stockholders are first paid (i) all dividends accrued and not yet paid plus (ii) the product of (a) dividends declared on an as converted basis and (b) Preferred Stock on an as converted basis. That is, if the Company declared dividends on outstanding common stock, Preferred Stockholders would receive both the dividends owed for the Preferred Stock plus that which would be owed if the Preferred Stock were converted to common stock. No dividends have been declared through December 31, 2020.

Voting Rights: Each holder of outstanding shares of Preferred Stock shall be entitled to cast the number of votes equal to the number of whole shares of common stock into which the shares of Preferred Stock held by such holder are convertible as of the record date for determining stockholders entitled to vote on such matter. Preferred stockholders and common stockholders vote together as a single class.

Common Stock

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Common Stock

COMMON STOCK

As of December 31, 2020, the Company’s certificate of incorporation authorized the Company to issue 200,000,000 shares of $0.0001 par value common stock.

In conjunction with the Company's April 2020 IPO closing, the Company issued and sold 6,900,000 shares of its common stock, including 900,000 shares pursuant to the full exercise of the underwriters option to purchase additional shares, at a public offering price of $16.00 per share, for aggregate net proceeds of $100.1 million after deducting underwriting discounts and commissions and offering costs. In connection with the IPO, all outstanding shares of Preferred Stock converted into 10,725,129 shares of common stock.

In conjunction with the Company's November 2020 public offering closing, the Company issued and sold 2,990,000 shares of its common stock, which includes 390,000 shares pursuant to the full exercise of the underwriters option to purchase additional shares, at a public offering price of $50.00 per share, for aggregate net proceeds of $140.1 million after deducting underwriting discounts and commissions and offering costs.

The following is a summary of the rights and privileges of the holders of common stock as of December 31, 2020:

Liquidation Preference: In the event of liquidation, dissolution or winding up, holders of common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then-outstanding shares of preferred stock.

Dividends: Subject to preferences that may be applicable to any then-outstanding preferred stock, holders of common stock are entitled to receive ratably those dividends, if any, as may be declared from time to time by the Board out of legally available funds. As of December 31, 2020, no cash dividends have been declared or paid.

Voting Rights: Each holder of common stock is entitled to one vote for each share on all matters submitted to a vote of the stockholders, including the election of directors. Under the Company's amended and restated certificate of incorporation and amended and restated bylaws, stockholders will not have cumulative voting rights. Because of this, the holders of a majority of the shares of common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they should so choose.

Rights and Preferences: Holders of common stock have no preemptive, conversion or subscription rights and there are no redemption or sinking fund provisions applicable to the common stock. The rights, preferences and privileges of the holders of common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that the Company may designate in the future.

As of December 31, 2020 and 2019, the Company has reserved the following shares of common stock for potential conversion of outstanding Preferred Stock, the vesting of restricted stock and exercise of stock options:



	DECEMBER 31,
	2020	2019
Preferred Stock	—	6,555,307
Unvested restricted stock	—	34,557
Options to purchase common stock	2,499,603	1,164,017
Total	2,499,603	7,753,881

Stock-Based Compensation

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

STOCK-BASED COMPENSATION

2017 Stock Incentive Plan

The Board adopted the 2017 Stock Incentive Plan (the "2017 Plan") in February 2017, and the stockholders approved the 2017 Plan in March 2017. The 2017 Plan was most recently amended in March 2020.

As of December 31, 2020, there were an aggregate of 1,047,512 shares of common stock issuable upon the exercise of outstanding options under the 2017 Plan. Any options or awards outstanding under the 2017 Plan remain outstanding and effective.

2020 Equity Incentive Plan

In April 2020, the 2020 Equity Incentive Plan (the "2020 Plan") became effective, and, as a result, no further awards will be made under the 2017 Plan. The 2020 Plan provides for the grant of stock options qualifying as incentive stock options ("ISOs"), to employees and for the grant of nonstatutory stock options ("NSOs"), restricted stock awards, restricted stock unit awards, stock appreciation rights, performance stock awards and other forms of stock compensation to employees, consultants and directors. The 2020 Plan also provides for the grant of performance cash awards to employees, consultants and directors. Any previously granted awards under the 2017 Plan will remain outstanding in accordance with their respective terms.

In March 2020, the Board approved an aggregate of 1,991,530 options under the 2020 Plan. No shares of common stock have been issued under the 2020 Plan. As of December 31, 2020, the number of shares of common stock

reserved for issuance under the 2020 Plan was 1,991,530. The number of shares of common stock initially reserved for issuance under the 2020 Plan is the sum of (i) 1,002,874 new shares of common stock, plus (ii) an additional number of shares not to exceed 2,104,937 shares, consisting of (A) the number of shares remaining available for issuance under the 2017 Plan when the 2020 Plan became effective and (B) the number of shares of common stock subject to outstanding awards under the 2017 Plan when the 2020 Plan became effective that thereafter expire or are forfeited, canceled, withheld to satisfy tax withholding or to purchase or exercise an award, reacquired by the Company or are otherwise terminated. The number of shares of common stock reserved for issuance under the 2020 Plan will automatically increase on January 1 of each year, for a period of ten years, from January 1, 2021 continuing through January 1, 2030, by 4.0% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Board. Accordingly, on January 1, 2021, 927,714 shares were added to the number of available shares under the 2020 Plan. The awards granted under the 2020 Plan typically vest over a four-year period and have a 10-year contractual term.

As of December 31, 2020, there were an aggregate of 1,452,091 shares of common stock issuable upon the exercise of outstanding options under the 2020 Plan. Additionally, there were an aggregate of 539,439 shares reserved for future issuance under the 2020 Plan.

Stock Option Valuation

The assumptions that the Company used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted for the years ended December 31, 2020 and 2019 were as follows:



	YEAR ENDED DECEMBER 31,
	2020			2019
Weighted-average risk-free interest rate	0.53		%	1.99		%
Expected term (in years)	6.06			6.05
Expected volatility	99.10		%	74.71		%
Expected dividend yield	0.00		%	0.00		%
Fair value of underlying common stock	$	15.57		$	0.32

A summary of option activity during the years ended December 31, 2020 and 2019 is as follows (in thousands except share and per share data):



	NUMBER OF OPTIONS	WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)	AGGREGATE INTRINSIC VALUE
Outstanding as of January 1, 2020	1,164,017	$	0.35	8.64	$	144
Granted	1,452,091	20.00
Exercised	(113,475)	0.34			$	3,349
Cancelled or forfeited	(3,030)	0.16
Outstanding as of December 31, 2020	2,499,603	$	11.77	8.62	$	147,103
Options exercisable as of December 31, 2019	608,156	$	0.29	8.17	$	112
Options exercisable as of December 31, 2020	723,130	$	0.57	7.38	$	50,599

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

The weighted-average grant date fair value price per share of options granted during each of the years ended December 31, 2020 and 2019 was $15.57 and $0.32, respectively. As of December 31, 2020, there was $18.7 million and of unrecognized stock-based compensation expense related to unvested stock options. The unrecognized stock-based compensation expense is estimated to be recognized over a period of 3.02 years.

The total fair value of options vested during the year ended December 31, 2020 was $0.2 million.

Shares of Restricted Common Stock

The Company has granted shares of restricted common stock with time-based vesting conditions. A summary of restricted stock activity under the 2017 Plan during the years ended December 31, 2020 and 2019 is as follows:



	YEAR ENDED DECEMBER 31,
	2020	2019
Unvested at the beginning of the year	34,557	138,227
Vested or released	(34,557)	(103,670)
Unvested at the end of the year	—	34,557

As of December 31, 2020, there was $0 of unrecognized stock-based compensation expense related to unvested restricted stock.

The total fair value of restricted stock vested during the year ended December 31, 2020 was not material.

Stock-Based Compensation Expense

Total stock-based compensation expense recorded as research and development and general and administrative expenses, respectively, for employees, directors and non-employees during the years ended December 31, 2020 and 2019 is as follows (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
Research and development	$	1,322	$	31
General and administrative	2,775		28
Total stock-based compensation expense	$	4,097	$	59

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

INCOME TAXES

Loss before benefit from income taxes for the years ended December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
United States	$	(31,898)	$	(5,563)
Foreign	(13,635)		(6,773)
Loss before benefit from income taxes	$	(45,533)	$	(12,336)

The components of income tax benefit for the years ended December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
Current income tax benefit:
United States	$	(172)	$	—
Total income tax benefit	$	(172)	$	—
Total deferred income tax benefit	$	—	$	—
Total income tax benefit	$	(172)	$	—

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended December 31, 2020 and 2019 was as follows:



	YEAR ENDED DECEMBER 31,
	2020		2019
Federal income tax at statutory rate	21.0	%	21.0	%
State income tax, net of federal benefit	4.7		3.9
Permanent Differences	(1.4)		(0.9)
Preferred stock tranche obligation remeasurement	(0.7)		(4.4)
Research and development credits	1.5		(2.1)
Impact of Foreign Operations	2.0		3.6
Other	(0.3)		—
Change in valuation allowance	(26.4)		(21.1)
Effective tax rate	0.4	%	0.0	%

Net deferred tax assets as of December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
Net operating loss carryforwards	$	10,324	$	3,127
Research and development credits	2,766		1,325
Accrueds	639		525
Other	4,319		1,180
Intangibles	139		151
Total deferred tax assets	$	18,187	$	6,308
Valuation allowance	(17,938)		(5,923)
Net deferred tax assets	$	249	$	385
Deferred tax liability
Depreciation	(249)		(385)
Net deferred tax assets (liability)	$	—	$	—

As of December 31, 2020, the Company had U.S. federal, state and foreign net operating loss carryforwards of $37.7 million, $25.9 million and $15.7 million, respectively. The federal and foreign net operating losses can be carried forward indefinitely. The state net operating loss carryforwards begin to expire in 2039.

As of December 31, 2020, the Company had U.S. federal and state research and development tax credit carryforwards of $1.8 million and $1.2 million, respectively. As of December 31, 2019, the Company had U.S. federal and state research and development tax credit carryforwards of $0.3 million and $0.3 million, respectively. The tax credits begin to expire in 2038.

Under the provisions of the Internal Revenue Code of 1986, as amended (the “Code”), the net operating loss and tax credit carryforwards are subject to review and potential adjustments by the Internal Revenue Services and state tax authorities. Under Section 382 of the Code (“Section 382”), certain substantial changes in the Company’s ownership, including the sale of the Company or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of net operating loss carryforwards or tax credits which could be used annually to offset future taxable income. The Company completed an analysis under Section 382 through November 17, 2020 and determined that on April 15, 2016 and April 13, 2020, ownership changes had occurred. Based on the Company’s analysis, the Company has determined that $0.3 million and $0.3 million of its federal and state net operating loss carryforwards, respectively, are limited by Section 382 as of December 31, 2020 and have been written off in the current period. The remaining unused carryforwards remain available for future periods. The Company may also experience ownership changes in the future as a result of subsequent shifts in the Company’s stock ownership, some of which may be outside the Company’s control. As a result, its ability to use its pre-change NOLs or tax credits to offset U.S. federal taxable income may be subject to limitations, which could potentially result in increased future tax liability. In addition, at

the state level, there may be periods during which the use of NOLs is suspended or otherwise limited, which could accelerate or permanently increase state taxes owed.

Management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of research and development credits and net operating losses. Under the applicable accounting standards, management has considered the Company’s history of losses and concluded that it is more likely than not that the Company will not recognize the benefits of federal and state deferred tax assets. Accordingly, a full valuation allowance was maintained as of December 31, 2020 and 2019. A change in the Company’s valuation allowance was recorded in 2020 and 2019, in the amount of $12.0 million and $2.6 million, respectively, due primarily to the generation of additional net deferred tax assets.

The calculation of the Company’s tax liabilities involves dealing with uncertainties in the application of complex tax laws and regulations for both federal taxes and the many states in which it operates or does business in. A tax benefit from an uncertain tax position may be recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, on the basis of the technical merits.

The Company records tax positions as liabilities and adjusts these liabilities when its judgement changes as a result of the evaluation of new information not previously available. Because of the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the Company’s current estimate of the recognized tax benefit liabilities. These differences will be reflected as increases or decreases to income tax expense in the period in which new information is available. As of December 31, 2020, the Company has not recorded any uncertain tax positions in its financial statements.

The Company recognizes interest and penalties related to unrecognized tax benefits on the income tax expense line in the accompanying consolidated statement of operations. As of December 31, 2020, no accrued interest or penalties are included on the related tax liability line in the consolidated balance sheet.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company’s tax years are still open under statute from December 31, 2015, to the present. There are currently no pending income tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future period.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Loss Per Share

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Loss Per Share

LOSS PER SHARE

Basic and diluted loss per share is computed by dividing net loss attributable to common stockholders by the weighted-average common shares outstanding (in thousands, except share and per share data):



	YEAR ENDED DECEMBER 31,
	2020		2019
Numerator:
Net loss	$	(45,361)	$	(12,336)
Less: accruals of dividends of preferred stock	—		(1,800)
Net loss attributable to common stockholders—basic and diluted	$	(45,361)	$	(14,136)
Denominator:
Weighted-average common stock outstanding	15,506,397		2,326,857
Net loss per share attributable to common stockholders—basic and diluted	$	(2.93)	$	(6.08)

The Company’s potentially dilutive securities, which include Preferred Stock, restricted stock, and stock options, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following from the

computation of diluted net loss per share attributable to common stockholders at December 31, 2020 and 2019 because including them would have had an anti-dilutive effect:



	DECEMBER 31,
	2020	2019
Preferred stock	—	6,555,307
Unvested restricted stock	—	34,557
Options to purchase common stock	2,499,603	1,164,017
	2,499,603	7,753,881

Commitment and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

COMMITMENTS AND CONTINGENCIES

Leases

The Company has historically entered into lease arrangements for its facilities and certain equipment. As of December 31, 2020, the Company had one operating lease with required future payments, related to its real estate. In applying the transition guidance under ASU No. 2016-02, Leases (Topic 842) (“ASC 842”), early adopted by the Company effective March 1, 2017, the Company determined the classification of its real estate lease to be operating and recorded a ROU asset and lease liability as of the effective date.

Operating Leases

In March 2017, the Company entered into a lease agreement (the “Lexington Lease”) for its headquarters located in Lexington, Massachusetts. In July and August 2019, the Company entered into the first and second amendment, respectively, to its Lexington Lease to expand the rental space to 10,417 square feet. As required under the term of the lease agreement as collateral for the facility lease, the Company had restricted cash of $0.1 million in the form of a certificate of deposit as of December 31, 2020 and 2019. The Lexington Lease provides for scheduled annual rent increases throughout the lease term and does not include termination or purchase options.

From time to time, leases may include options to renew the lease after the expiration of the initial lease term. A renewal period is included in the lease term only when it is reasonably certain that the Company will exercise such renewal options. As of December 31, 2020, no renewal options existed that the Company believed were reasonably certain of being exercised.

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating lease for the years ended December 31, 2020 and 2019 (in thousands):



	FOR THE YEARS ENDED DECEMBER 31,
	2020			2019
Lease cost
Operating lease cost	$	468		$	278
Total lease cost	$	468		$	278
Other information
Operating lease payments	$	468		$	278
Remaining lease term	1.9 years			2.9 years
Discount rate	8.02		%	8.02		%

The Lexington Lease does not include any variable payments. As the Lexington Lease does not provide an implicit rate, the Company utilized its incremental borrowing rate based on what it would normally pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments at the commencement date in determining the present value of lease payments. As of December 31, 2020 and 2019, the Company classified its short-term and long-term operating liabilities as short-term and long-term liabilities on the consolidated balance sheet, respectively.

As of December 31, 2020, future discounted lease payments under all lease arrangements accounted for under ASC 842 were as follows (in thousands):



MATURITY OF LEASE LIABILITY
2021	$	482
2022	497
Total lease payments	979
Less: imputed interest	(80)
Total operating lease liabilities	$	899
Included in the consolidated balance sheet:
Current portion of lease liabilities	$	423
Lease liabilities	476
Total operating lease liabilities	$	899

Short-term Leases

The Company enters into short-term leasing arrangements related to storage of clinical trial materials. The Company has $36,290 and $1,544 related to rent expense for the years ended December 31, 2020 and 2019. As of December 31, 2020 and 2019, the Company classified its short-term operating lease liabilities within accrued expenses and other current liabilities, as the Company has elected the practical expedient whereby it will not recognize leases with terms of 12 months or less on the balance sheet.

Legal Proceedings

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Other

In connection with the Lexington Lease entered into in March 2017, the Company received a loan from the landlord of $0.2 million related to its tenant improvement allowance, which is recorded as a non-current liability in the Company’s consolidated balance sheets. The Company is required to repay interest only on the loan of 8.0% for the first 18 months of the lease and will then repay the full amount plus interest in installments over the remaining 3.5 year term of the lease, which expires in December 2022. The Company made payments totaling $65,000 related to the loan in 2020.

Future payments under the Company’s loan obligation as of December 31, 2020, are as follows (in thousands):



2021	$	65
2022	65
Total payments	$	130

Refer to Note 7, License Agreements, for any potential future milestone or royalty payment amounts. These are not currently probable or estimable.

Revenue from Contracts with Customers	12 Months Ended
Revenue from Contracts with Customers	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	REVENUE FROM CONTRACTS WITH CUSTOMERS The Company adopted ASC Topic 606 on January 1, 2018 applying the full retrospective method to all contracts that were not completed as of January 1, 2018. While the timing of future revenue under ASC Topic 606 may differ from the Company’s historical accounting practices under ASC Topic 605, the cumulative effect recognized in the consolidated statement of stockholder’s equity (deficit) was $0 because there was no change in timing or measurement of revenue for open contracts at January 1, 2018. Novo Nordisk Agreement Background On December 14, 2017, the Company entered into a research collaboration and exclusive license agreement with Novo Nordisk A/S (“Novo,” agreement referred to as the “Novo Agreement”). The Novo Agreement stipulates that the two parties will work together on the discovery and development of new ligand traps for two years. Under the Novo Agreement, Keros granted Novo an exclusive license to develop and commercialize the licensed products listed as part of Keros’ intellectual property and Novo granted Keros a non-exclusive license to Novo’s intellectual property so that Keros could perform the activities for which it is responsible under the Novo Agreement. The Company does not share in the rights to the results of the Novo Agreement. On October 26, 2020, Novo provided the Company with written notice of termination of the Novo Agreement, effective April 26, 2021. Upon the termination of the Novo Agreement, the license granted by the Company to Novo will be automatically terminated. Accordingly, the Company's singular performance obligation will be fully satisfied upon termination. Novo Nordisk is obligated to continue to reimburse the Company for certain research and development costs through April 26, 2021. Upon effectiveness of the termination, such reimbursements will cease. Accounting Treatment As consideration, the Company received an initial license payment in 2018 from Novo in the amount of $16.0 million. Novo has also paid the Company research collaboration budget funding payments of $2.0 million per each collaboration year, for $4.0 million total. Both of these research collaboration budget funding payments were received in 2018. Additionally, there are performance-based and sales-based milestone payments and sales-based royalties that have been determined to be variable consideration and constrained due to uncertainty of achievement. The sales-based royalties will be included in the transaction price and recognized as revenue once a sale occurs, and performance-based and sales-based milestone payments will be included in the transaction price and recognized as revenue if and when the cumulative revenue associated with the consideration is no longer probable of significant reversal. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Novo, is a customer. The Company identified the following material promises at the outset of the Novo Agreement: (1) an exclusive license to use the Company’s intellectual property to conduct research activities; (2) research and development (“R&D”) services for activities under the research plan; (3) an option to extend the Novo Agreement; (4) participation on the joint steering committee (“JSC”); and (5) technology transfer associated with the research and development outputs. The Company determined that these promises were not capable of being distinct from one another and were not distinct in the context of the contract, as the license has no true value without the performance of the R&D activities and the technology transfer and JSC participation depend on these activities. Novo would not be able to use the license without the performance of R&D activities by the Company, as the research is novel in nature and could not be performed by another company. Additionally, the technology transfer is inherently dependent on the outcome of the Company’s R&D activities, and as such is not capable of being distinct. As indicated in number (3) above, Novo may elect to extend the term of the Novo Agreement to a third year on similar terms and conditions, subject to mutual written agreement of Novo and the Company. The Company assessed this option as a potential material right and determined that the additional work would be performed based on negotiated rates at the standalone selling price, and as such these services would not be provided at a significant or incremental discount and the option does not provide Novo with a material right. The Novo Agreement did not contain a significant financing component as of December 31, 2020 and 2019. In accordance with the Company’s ASC 606 assessment, the Novo Agreement was determined to contain a single combined performance obligation made up of the promises above, which does not require further allocation as the entire transaction price is allocated to this performance obligation. The Company determined the contract term of the Novo Agreement to be two years. The Company identified an appropriate measure of progress for the recognition of revenue and determined it would recognize the revenue over the term of the Novo Agreement using an input method based on full-time employee (“FTE”) costs incurred, as this appropriately depicts the Company’s performance in satisfaction of the performance obligation. As such, the Company is recognizing the transaction price for its single performance obligation as Novo uses the license and research and development services performed by the Company and as the Company participates on the JSC. Amounts received that have not yet been recognized as revenue are recorded in deferred revenue on the Company’s consolidated balance sheet. The Company recognized $0 and $10.0 million for the years ended December 31, 2020 and 2019, respectively, related to the Novo Agreement. As of December 31, 2019, there was no remaining revenue or deferred revenue to be recognized under the Novo Agreement.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTSIn March 2021, the Company signed a license agreement for approximately 2,550 square feet of office and laboratory space to expand our principal office, with a commencement date of March 18, 2021. This agreement expires in September 2021, unless earlier terminated. Under the agreement, the Company is required to make monthly payments of $14,000.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of Accounting

The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and its wholly owned subsidiaries, Keros Therapeutics Australia Pty Ltd (“Keros Australia”) and Keros Security Corporation, a Massachusetts securities corporation.

Principles of Consolidation

Use of Estimates

Fair Value Measurements

Level 1—Quoted prices in active markets for identical assets or liabilities.

Cash, Cash Equivalents, and Restricted Cash

Deferred Offering Costs

Deferred Offering CostsThe Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity (deficit) as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations.

Concentrations of Credit Risk

Property and Equipment



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Impairment of Long-Lived Assets

Impairment of Long-Lived AssetsThe Company evaluates its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell.

Leases

For all asset classes of its leases, the Company has elected to account for the lease and non-lease components together for existing classes of underlying assets.

Guarantees and Indemnifications

Guarantees and IndemnificationsAs permitted under Delaware law, the Company indemnifies its officers, directors, consultants and employees for certain events or occurrences that happen by reason of the relationship with, or position held at, the Company.

Research and Development Costs

Research and Development Incentive and Income Taxes

Research and Development Incentive

The Australian research and development tax incentive program provides tax offsets to eligible companies that engage in research and development activities and has two core components:

▪43.5% refundable tax offset for certain eligible research and development entities with an aggregated turnover of less than $20.0 million per annum; and

▪38.5% non-refundable tax offset for all other eligible research and development entities. Unused offset amounts may be able to be carried forward for use in future income years.

Income Taxes

Revenue Recognition

To date, the Company has earned revenue solely under the license agreement with Novo Nordisk A/S, which was terminated in October 2020 (see Note 14).

development costs; development, clinical, regulatory and commercial sales milestone payments, and royalties on net sales of licensed products.

Foreign Currency Transactions

Segment Information

Segment InformationOperating segments are identified as components of an enterprise about which separate discrete financial information is made available for evaluation by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The CODM is the Company’s chief executive officer. The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular concentration is focused on the discovery and development of breakthrough therapeutics for hematological and musculoskeletal disorders with high unmet medical need.

Common Stock Valuation

Common Stock ValuationPrior to the Company’s IPO in April 2020, due to the absence of an active market for the Company’s common stock, the Company utilized methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid (Valuation of Privately-Held Company Equity Securities Issued as Compensation) to estimate the fair value of its common stock. Prior to the IPO, the fair value of the shares of common stock underlying the stock-based awards were determined by the Board with input from management. Since there was no public market for the common stock prior to April 8, 2020, the Board had determined the fair value of the common stock at the time of grant of the stock-based award by considering a number of objective and subjective factors, including having valuations of the common stock performed by a third-party valuation specialist. Following the closing of the initial public offering, the fair value of the Company’s common stock is determined based on the quoted market price of the common stock.

Convertible Preferred Stock

Stock-Based Compensation

Comprehensive Loss

Net Loss Per Share

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Summary of Estimated Useful Lives

Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Property and equipment, net as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Computer equipment and software	$	35	$	35
Laboratory equipment	1,106		843
Office furniture	47		42
Leasehold improvements	257		241
Total	1,445		1,161
Less: accumulated depreciation	(721)		(453)
Property and equipment, net	$	724	$	708

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis




DESCRIPTION	DECEMBER 31, 2020		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	262,043	$	262,043	$	—	$	—
Total financial assets	$	262,043	$	262,043	$	—	$	—




DESCRIPTION	DECEMBER 31, 2019		QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)		SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	$	4,972	$	4,972	$	—	$	—
Total financial assets	$	4,972	$	4,972	$	—	$	—
Liability
Preferred stock tranche obligation	$	(4,956)	$	—	$	—	$	(4,956)
Total financial liabilities	$	(4,956)	$	—	$	—	$	(4,956)

Fair Value Measurement Inputs and Valuation Techniques

The following reflects the significant quantitative inputs used in the valuation of the Preferred Stock Tranche Obligation:



	MARCH 2, 2020			DECEMBER 31, 2019
Stand-alone Series B-1 Preferred Stock price (spot price)	$	7.28		$	7.28
Estimated future value of Series B-2 Preferred Stock	$	8.14		$	8.14
Discount rate	15.50		%	15.50		%
Time to liquidity (years)	0.00			0.16
Probability of tranche closing	100		%	80		%

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation

The following table sets forth a summary of changes in the fair value of the Company’s Preferred Stock Tranche Obligation for which fair value was determined by Level 3 inputs (in thousands):



	PREFERRED STOCK TRANCHE OBLIGATION
Balance as of January 1, 2019	$	2,392
Issuance	—
Change in fair value	2,564
Balance as of December 31, 2019	4,956
Change in fair value	1,490
Settlement of tranche obligation	(6,446)
Balance as of December 31, 2020	$	—

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2020

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Summary of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Prepaid service contracts	501		21
Income tax credit receivable	172		—
Prepaid sales tax	188		65
Prepaid rent	—		64
R&D payroll tax credit	44		—
Prepaid Insurance	785		16
Other	160		215
Total prepaid expenses and other current assets	$	1,850	$	381

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2020

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

Depreciation is calculated using the straight-line method over the estimated useful lives of the related assets as follows:



			ESTIMATED USEFUL LIFE
Computer equipment and software			3 years
Laboratory equipment			5 years
Office furniture			5 years
Leasehold improvements			lesser of useful life or remaining lease term

Property and equipment, net as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Computer equipment and software	$	35	$	35
Laboratory equipment	1,106		843
Office furniture	47		42
Leasehold improvements	257		241
Total	1,445		1,161
Less: accumulated depreciation	(721)		(453)
Property and equipment, net	$	724	$	708

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2020

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of December 31, 2020 and 2019 consisted of the following (in thousands):



	DECEMBER 31,
	2020		2019
Accrued external R&D costs	$	169	$	645
Accrued external manufacturing costs	2,265		282
Accrued compensation and benefits	1,510		749
Accrued tax	185		43
Accrued legal and consultants	265		34
Other	218		269
Total accrued expenses and other current liabilities	$	4,612	$	2,022

Convertible Preferred Stock (Tables)

12 Months Ended

Dec. 31, 2020

Temporary Equity Disclosure [Abstract]

Summary of Preferred Stock

As of December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data):



	DECEMBER 31, 2019
	PREFERRED STOCK AUTHORIZED	PREFERRED STOCK ISSUED AND OUTSTANDING	CARRYING VALUE		LIQUIDATION VALUE		COMMON STOCK ISSUABLE UPON CONVERSION
Series A Preferred Stock	10,000,000	4,607,652	$	9,891	$	12,271	4,607,652
Series A1 Preferred Stock	800,000	368,612	944		1,171		368,612
Series B1 Preferred Stock	3,427,004	1,579,043	9,106		12,596		1,579,043
Series B2 Preferred Stock	3,062,891	—	—		—		—
	17,289,895	6,555,307	$	19,941	$	26,038	6,555,307



	DECEMBER 31,
	2020	2019
Preferred Stock	—	6,555,307
Unvested restricted stock	—	34,557
Options to purchase common stock	2,499,603	1,164,017
Total	2,499,603	7,753,881

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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+ Details

Common Stock (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Summary of Common Stock Reserved for Potential Conversion of Outstanding Preferred Stock and Vesting of Restricted Stock and Exercise of Stock Options

As of December 31, 2019, Preferred Stock consisted of the following (in thousands, except share data):



	DECEMBER 31, 2019
	PREFERRED STOCK AUTHORIZED	PREFERRED STOCK ISSUED AND OUTSTANDING	CARRYING VALUE		LIQUIDATION VALUE		COMMON STOCK ISSUABLE UPON CONVERSION
Series A Preferred Stock	10,000,000	4,607,652	$	9,891	$	12,271	4,607,652
Series A1 Preferred Stock	800,000	368,612	944		1,171		368,612
Series B1 Preferred Stock	3,427,004	1,579,043	9,106		12,596		1,579,043
Series B2 Preferred Stock	3,062,891	—	—		—		—
	17,289,895	6,555,307	$	19,941	$	26,038	6,555,307



	DECEMBER 31,
	2020	2019
Preferred Stock	—	6,555,307
Unvested restricted stock	—	34,557
Options to purchase common stock	2,499,603	1,164,017
Total	2,499,603	7,753,881

- Definition

+ References

+ Details

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Valuation Assumptions



	YEAR ENDED DECEMBER 31,
	2020			2019
Weighted-average risk-free interest rate	0.53		%	1.99		%
Expected term (in years)	6.06			6.05
Expected volatility	99.10		%	74.71		%
Expected dividend yield	0.00		%	0.00		%
Fair value of underlying common stock	$	15.57		$	0.32

Summary of Option Activity

A summary of option activity during the years ended December 31, 2020 and 2019 is as follows (in thousands except share and per share data):



	NUMBER OF OPTIONS	WEIGHTED- AVERAGE EXERCISE PRICE		WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)	AGGREGATE INTRINSIC VALUE
Outstanding as of January 1, 2020	1,164,017	$	0.35	8.64	$	144
Granted	1,452,091	20.00
Exercised	(113,475)	0.34			$	3,349
Cancelled or forfeited	(3,030)	0.16
Outstanding as of December 31, 2020	2,499,603	$	11.77	8.62	$	147,103
Options exercisable as of December 31, 2019	608,156	$	0.29	8.17	$	112
Options exercisable as of December 31, 2020	723,130	$	0.57	7.38	$	50,599

Summary of Restricted Stock Activity

A summary of restricted stock activity under the 2017 Plan during the years ended December 31, 2020 and 2019 is as follows:



	YEAR ENDED DECEMBER 31,
	2020	2019
Unvested at the beginning of the year	34,557	138,227
Vested or released	(34,557)	(103,670)
Unvested at the end of the year	—	34,557

Schedule of Stock-based Compensation Expense



	YEAR ENDED DECEMBER 31,
	2020		2019
Research and development	$	1,322	$	31
General and administrative	2,775		28
Total stock-based compensation expense	$	4,097	$	59

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Loss Before Provision For (Benefit From) Income Taxes

Loss before benefit from income taxes for the years ended December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
United States	$	(31,898)	$	(5,563)
Foreign	(13,635)		(6,773)
Loss before benefit from income taxes	$	(45,533)	$	(12,336)

Schedule of Components of Income Tax Expense (Benefit)

The components of income tax benefit for the years ended December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
Current income tax benefit:
United States	$	(172)	$	—
Total income tax benefit	$	(172)	$	—
Total deferred income tax benefit	$	—	$	—
Total income tax benefit	$	(172)	$	—

Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended December 31, 2020 and 2019 was as follows:



	YEAR ENDED DECEMBER 31,
	2020		2019
Federal income tax at statutory rate	21.0	%	21.0	%
State income tax, net of federal benefit	4.7		3.9
Permanent Differences	(1.4)		(0.9)
Preferred stock tranche obligation remeasurement	(0.7)		(4.4)
Research and development credits	1.5		(2.1)
Impact of Foreign Operations	2.0		3.6
Other	(0.3)		—
Change in valuation allowance	(26.4)		(21.1)
Effective tax rate	0.4	%	0.0	%

Schedule of Net Deferred Tax Assets

Net deferred tax assets as of December 31, 2020 and 2019 consisted of the following (in thousands):



	YEAR ENDED DECEMBER 31,
	2020		2019
Net operating loss carryforwards	$	10,324	$	3,127
Research and development credits	2,766		1,325
Accrueds	639		525
Other	4,319		1,180
Intangibles	139		151
Total deferred tax assets	$	18,187	$	6,308
Valuation allowance	(17,938)		(5,923)
Net deferred tax assets	$	249	$	385
Deferred tax liability
Depreciation	(249)		(385)
Net deferred tax assets (liability)	$	—	$	—

Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Basic and Diluted Loss Per Share Calculation



	YEAR ENDED DECEMBER 31,
	2020		2019
Numerator:
Net loss	$	(45,361)	$	(12,336)
Less: accruals of dividends of preferred stock	—		(1,800)
Net loss attributable to common stockholders—basic and diluted	$	(45,361)	$	(14,136)
Denominator:
Weighted-average common stock outstanding	15,506,397		2,326,857
Net loss per share attributable to common stockholders—basic and diluted	$	(2.93)	$	(6.08)

Schedule of Antidilutive Securities Excluded From Computation of Diluted Net Loss Per Share

The Company excluded the following from the

computation of diluted net loss per share attributable to common stockholders at December 31, 2020 and 2019 because including them would have had an anti-dilutive effect:



	DECEMBER 31,
	2020	2019
Preferred stock	—	6,555,307
Unvested restricted stock	—	34,557
Options to purchase common stock	2,499,603	1,164,017
	2,499,603	7,753,881

Commitment and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments and Contingencies Disclosure [Abstract]

Summary of Lease Costs



	FOR THE YEARS ENDED DECEMBER 31,
	2020			2019
Lease cost
Operating lease cost	$	468		$	278
Total lease cost	$	468		$	278
Other information
Operating lease payments	$	468		$	278
Remaining lease term	1.9 years			2.9 years
Discount rate	8.02		%	8.02		%

Maturity of Lease Liability

As of December 31, 2020, future discounted lease payments under all lease arrangements accounted for under ASC 842 were as follows (in thousands):



MATURITY OF LEASE LIABILITY
2021	$	482
2022	497
Total lease payments	979
Less: imputed interest	(80)
Total operating lease liabilities	$	899
Included in the consolidated balance sheet:
Current portion of lease liabilities	$	423
Lease liabilities	476
Total operating lease liabilities	$	899

Future Payments Under Loan Obligation

Future payments under the Company’s loan obligation as of December 31, 2020, are as follows (in thousands):



2021	$	65
2022	65
Total payments	$	130

Nature of Business and Basis of Presentation - Narrative (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Nov. 17, 2020 USD ($) shares	Apr. 13, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($)
Class of Stock [Line Items]
Issuance of initial public offering \| $	$ 149,500	$ 110,400	$ 102,672	$ 0
Proceeds from initial public offering, net of discounts and offering costs \| $	$ 140,100	$ 100,100
Common Stock
Class of Stock [Line Items]
Conversion of convertible preferred stock upon initial public offering (in shares)		10,725,129	10,725,129
IPO
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		6,900,000
Sale of stock, price per share (in USD per share) \| $ / shares		$ 16.00
Reverse stock split		0.4607658
Over-Allotment Option
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	390,000	900,000

Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands		12 Months Ended
	Apr. 13, 2020 shares	Dec. 31, 2020 USD ($) segment shares	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Money market funds		$ 262,000	$ 5,000
Restricted cash		115	115
Deferred offering costs		0	604
Research and development incentive receivable		0	900
Research and development incentive income		$ 2,460	$ 558
Number of operating segments \| segment		1
Conversion of Stock [Line Items]
Preferred stock authorized (in shares) \| shares	10,000,000
Preferred stock outstanding (in shares) \| shares		0
Common Stock
Conversion of Stock [Line Items]
Conversion of convertible preferred stock upon initial public offering (in shares) \| shares	10,725,129	10,725,129

Summary of Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2020
Computer equipment and software
Property, Plant and Equipment [Line Items]
ESTIMATED USEFUL LIFE	3 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years
Office furniture
Property, Plant and Equipment [Line Items]
ESTIMATED USEFUL LIFE	5 years

Fair Value Measurements - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Asset
Money market funds	$ 262,000	$ 5,000
Liability
Preferred stock tranche obligation	0	(4,956)
Fair Value, Recurring
Asset
Money market funds	262,043	4,972
Total financial assets	262,043	4,972
Liability
Preferred stock tranche obligation		(4,956)
Total financial liabilities		(4,956)
Fair Value, Recurring \| QUOTED PRICES ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset
Money market funds	262,043	4,972
Total financial assets	262,043	4,972
Liability
Preferred stock tranche obligation		0
Total financial liabilities		0
Fair Value, Recurring \| SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset
Money market funds	0	0
Total financial assets	0	0
Liability
Preferred stock tranche obligation		0
Total financial liabilities		0
Fair Value, Recurring \| SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 3)
Asset
Money market funds	0	0
Total financial assets	$ 0	0
Liability
Preferred stock tranche obligation		(4,956)
Total financial liabilities		$ (4,956)

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in fair value of preferred stock tranche obligation	$ 1,490	$ 2,564
Preferred Stock Tranche Obligation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Changes in fair value of preferred stock tranche obligation	1,490	2,564
Settlement of preferred stock tranche obligation	6,446
Preferred stock tranche obligation	$ 0	$ 4,956	$ 2,392

Fair Value Measurements - Significant Quantitative Inputs (Details)		12 Months Ended
	Mar. 02, 2020 $ / shares	Dec. 31, 2019 $ / shares
Stand-alone Series B-1 Preferred Stock price (spot price) \| Series B1 Preferred Stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input (in USD per share)	$ 7.28	$ 7.28
Estimated future value of Series B-2 Preferred Stock \| Series B2 Preferred Stock
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input (in USD per share)	$ 8.14	$ 8.14
Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, decimal	0.1550	0.1550
Time to liquidity (years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, term	0 years	1 month 28 days
Probability of tranche closing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Preferred stock tranche obligation, measurement input, decimal	1	0.80

Fair Value Measurements - Changes in Level 3 Fair Value Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in fair value	$ 1,490	$ 2,564
Preferred Stock Tranche Obligation
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	4,956	2,392
Issuance		0
Change in fair value	1,490	2,564
Settlement of tranche obligation	(6,446)
Ending balance	$ 0	$ 4,956

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid service contracts	$ 501	$ 21
Income tax credit receivable	172	0
Prepaid sales tax	188	65
Prepaid rent	0	64
R&D payroll tax credit	44	0
Prepaid Insurance	785	16
Other	160	215
Prepaid expenses and other current assets	$ 1,850	$ 381

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 1,445	$ 1,161
Less: accumulated depreciation	(721)	(453)
Property and equipment, net	724	708
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	35	35
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,106	843
Office furniture
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	47	42
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 257	$ 241

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 0.3	$ 0.2

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Accrued external R&D costs	$ 169	$ 645
Accrued external manufacturing costs	2,265	282
Accrued compensation and benefits	1,510	749
Accrued tax	185	43
Accrued legal and consultants	265	34
Other	218	269
Total accrued expenses and other current liabilities	$ 4,612	$ 2,022

License Agreements (Details) - USD ($) $ in Thousands			12 Months Ended
License Agreements (Details) - USD ($) $ in Thousands	Apr. 22, 2019	Apr. 05, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development			$ 33,860	$ 17,379
MGH \| License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Initial license payment						$ 100
Reimbursement of prior patent prosecution expenses					$ 300
Sale of stock, number of shares issued in transaction (in shares)		358,674
Clinical and regulatory milestone payments		$ 8,600
Commercial milestone payments		$ 18,000
Royalty rate, maximum reduction		50.00%
Expiration period		10 years
LakePharma \| License Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development	$ 300

Convertible Preferred Stock - Narrative (Details) - USD ($)			12 Months Ended
	Apr. 13, 2020	Mar. 02, 2020	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Shares authorized (in shares)				17,289,895
Issuance costs			$ 227,000	$ 0
Preferred stock authorized (in shares)	10,000,000
Preferred stock outstanding (in shares)			0
Conversion ratio (in shares)			1
Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock upon initial public offering (in shares)	10,725,129		10,725,129
Common Stock \| Dividend Declared
Temporary Equity [Line Items]
Dividends payable			$ 0
Series A Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)			0	10,000,000
Par value (in USD per share)			$ 0.0001	$ 0.0001
Conversion of convertible preferred stock upon initial public offering (in shares)			(4,607,652)
Preferred stock, dividend rate (in USD per share)			$ 0.17
Series A1 Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)			0	800,000
Par value (in USD per share)			$ 0.0001	$ 0.0001
Conversion of convertible preferred stock upon initial public offering (in shares)			(368,612)
Preferred stock, dividend rate (in USD per share)			$ 0.21
Series B1 Preferred Stock
Temporary Equity [Line Items]
Shares authorized (in shares)			0	3,427,004
Par value (in USD per share)			$ 0.0001	$ 0.0001
Conversion of convertible preferred stock upon initial public offering (in shares)			(1,579,043)
Preferred stock, dividend rate (in USD per share)			$ 0.582630
Series C preferred stock
Temporary Equity [Line Items]
Shares authorized (in shares)		9,049,783
Par value (in USD per share)		$ 0.0001	$ 0.0001
Sale of stock, number of shares issued in transaction (in shares)		4,169,822
Sale of stock, price per share (in USD per share)		$ 13.43
Gross proceeds from issuance of convertible preferred stock		$ 56,000,000.0
Issuance costs		$ 200,000
Conversion of convertible preferred stock upon initial public offering (in shares)			(4,169,822)
Preferred stock, dividend rate (in USD per share)			$ 0.651888
Series C preferred stock \| Affiliated Entity
Temporary Equity [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		3,078,968
Convertible Preferred Stock \| Dividend Declared
Temporary Equity [Line Items]
Dividends payable			$ 0

Convertible Preferred Stock - Summary of Preferred Stock (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)		17,289,895
PREFERRED STOCK ISSUED (in shares)		6,555,307
PREFERRED STOCK OUTSTANDING (in shares)		6,555,307
CARRYING VALUE		$ 19,941,000
LIQUIDATION VALUE		$ 26,038,000
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)		6,555,307
Series A Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	0	10,000,000
PREFERRED STOCK ISSUED (in shares)	0	4,607,652
PREFERRED STOCK OUTSTANDING (in shares)	0	4,607,652	4,607,652
CARRYING VALUE	$ 0	$ 9,891,000	$ 9,891,000
LIQUIDATION VALUE	$ 0	$ 12,271,000
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)		4,607,652
Series A1 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	0	800,000
PREFERRED STOCK ISSUED (in shares)	0	368,612
PREFERRED STOCK OUTSTANDING (in shares)	0	368,612	368,612
CARRYING VALUE	$ 0	$ 944,000	$ 944,000
LIQUIDATION VALUE	$ 0	$ 1,171,000
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)		368,612
Series B1 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)	0	3,427,004
PREFERRED STOCK ISSUED (in shares)	0	1,579,043
PREFERRED STOCK OUTSTANDING (in shares)	0	1,579,043	1,579,043
CARRYING VALUE	$ 0	$ 9,106,000	$ 9,106,000
LIQUIDATION VALUE	$ 0	$ 12,596,000
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)		1,579,043
Series B2 Preferred Stock
Temporary Equity [Line Items]
PREFERRED STOCK AUTHORIZED (in shares)		3,062,891
PREFERRED STOCK ISSUED (in shares)		0
PREFERRED STOCK OUTSTANDING (in shares)		0
CARRYING VALUE		$ 0
LIQUIDATION VALUE		$ 0
COMMON STOCK ISSUABLE UPON CONVERSION (in shares)		0

Common Stock - Narrative (Details)			12 Months Ended
Common Stock - Narrative (Details)	Nov. 17, 2020 USD ($) $ / shares shares	Apr. 13, 2020 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) vote $ / shares shares	Dec. 31, 2019 $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			200,000,000	27,000,000
Common stock, par value (in USD per share) \| $ / shares			$ 0.0001	$ 0.0001
Proceeds from initial public offering, net of discounts and offering costs \| $	$ 140,100,000	$ 100,100,000
Common stock issuable upon conversion (in shares)				6,555,307
Number of votes per common share held \| vote			1
IPO
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)		6,900,000
Sale of stock, price per share (in USD per share) \| $ / shares		$ 16.00
Over-Allotment Option
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	390,000	900,000
Public Offering
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	2,990,000
Sale of stock, price per share (in USD per share) \| $ / shares	$ 50.00
Common Stock
Class of Stock [Line Items]
Common stock issuable upon conversion (in shares)		10,725,129
Dividend Declared \| Common Stock
Class of Stock [Line Items]
Dividends payable \| $			$ 0

Common Stock - Summary of Common Stock Reserved for Future Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	2,499,603	7,753,881
Unvested restricted stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	0	34,557
Options to purchase common stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	2,499,603	1,164,017
Preferred Stock
Class of Stock [Line Items]
Common stock, reserved for future issuance (in shares)	0	6,555,307

Stock-Based Compensation - Narrative (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jan. 01, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, reserved for future issuance (in shares)			2,499,603	7,753,881
Options granted in period (in shares)			1,452,091
Weighted-average grant date fair value of options granted during the period (in dollars per share)			$ 15.57	$ 0.32
Unrecognized stock-based compensation expense related to unvested stock options			$ 18,700,000
Total fair value of options vested during period			200,000
Unrecognized stock-based compensation expense related to unvested restricted stock (less than)			$ 0
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, reserved for future issuance (in shares)			2,499,603	1,164,017
Unvested award, period for recognition			3 years 7 days
2017 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			1,047,512
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		1,991,530	1,991,530
Number of shares issued, common stock (in shares)			0
Common stock, reserved for future issuance (in shares)		1,002,874
Number of additional shares authorized (in shares)		2,104,937
Automatic increase period			10 years
Annual percentage increase in shares authorized			4.00%
Vesting period			4 years
Contractual term			10 years
Options granted in period (in shares)			1,452,091
Number of shares available for future grants (in shares)			539,439
2020 Plan \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (in shares)	927,714

Stock-Based Compensation - Stock Option Valuation (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average risk-free interest rate	0.53%	1.99%
Expected term (in years)	6 years 21 days	6 years 18 days
Expected volatility	99.10%	74.71%
Expected dividend yield	0.00%	0.00%
Fair value of underlying common stock (in USD per share)	$ 15.57	$ 0.32

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
NUMBER OF OPTIONS
Outstanding as of beginning of period (in shares)	1,164,017
Granted (in shares)	1,452,091
Exercised (in shares)	(113,475)
Cancelled or forfeited (in shares)	(3,030)
Outstanding as of end of period (in shares)	2,499,603	1,164,017
Options exercisable (in shares)	723,130	608,156
WEIGHTED- AVERAGE EXERCISE PRICE
Outstanding as of beginning of period (in USD per share)	$ 0.35
Granted (in USD per share)	20.00
Exercised (in USD per share)	0.34
Cancelled or forfeited (in USD per share)	0.16
Outstanding as of end of period (in USD per share)	11.77	$ 0.35
Options exercisable (in USD per share)	$ 0.57	$ 0.29
WEIGHTED-AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS)
Outstanding	8 years 7 months 13 days	8 years 7 months 20 days
Options exercisable	7 years 4 months 17 days	8 years 2 months 1 day
AGGREGATE INTRINSIC VALUE
Outstanding	$ 147,103	$ 144
Exercised	3,349
Options exercisable	$ 50,599	$ 112

Stock-Based Compensation - Restricted Stock Activity (Details) - Restricted Stock - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested at the beginning of the period (in shares)	34,557	138,227
Vested or released (in shares)	(34,557)	(103,670)
Unvested at the end of the period (in shares)	0	34,557

Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4,097	$ 59
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,322	31
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 2,775	$ 28

Income Taxes - Schedule of Loss Before Provision For (Benefit From) Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
United States	$ (31,898)	$ (5,563)
Foreign	(13,635)	(6,773)
Loss before benefit from income taxes	$ (45,533)	$ (12,336)

Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current income tax benefit:
United States	$ (172)	$ 0
Total income tax benefit	(172)	0
Total deferred income tax benefit	0	0
Total income tax benefit	$ (172)	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income tax at statutory rate	21.00%	21.00%
State income tax, net of federal benefit	4.70%	3.90%
Permanent Differences	(1.40%)	(0.90%)
Preferred stock tranche obligation remeasurement	(0.70%)	(4.40%)
Research and development credits	1.50%	(2.10%)
Impact of Foreign Operations	2.00%	3.60%
Other	(0.30%)	0.00%
Change in valuation allowance	(26.40%)	(21.10%)
Effective tax rate	0.40%	0.00%

Income Taxes - Schedule of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 10,324	$ 3,127
Research and development credits	2,766	1,325
Accrueds	639	525
Other	4,319	1,180
Intangibles	139	151
Total deferred tax assets	18,187	6,308
Valuation allowance	(17,938)	(5,923)
Net deferred tax assets	249	385
Deferred tax liability
Depreciation	(249)	(385)
Net deferred tax assets (liability)	$ 0	$ 0

Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Tax Credit Carryforward [Line Items]
Change in valuation allowance	$ 12.0	$ 2.6
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	37.7
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards written off in the current period	0.3
Federal \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	1.8	0.3
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	25.9
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards written off in the current period	0.3
State \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	1.2	$ 0.3
Foreign
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 15.7

Loss Per Share - Basic and Diluted Loss Per Share Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss	$ (45,361)	$ (12,336)
Less: accruals of dividends of preferred stock	0	(1,800)
Net loss attributable to common stockholders—basic and diluted	$ (45,361)	$ (14,136)
Denominator:
Weighted-average common stock outstanding (in shares)	15,506,397	2,326,857
Net loss per share attributable to common stockholders - basic and diluted (in USD per share)	$ (2.93)	$ (6.08)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

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+ Details

Loss Per Share - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,499,603	7,753,881
Preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	6,555,307
Unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	34,557
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	2,499,603	1,164,017

Commitment and Contingencies - Narrative (Details)	1 Months Ended	12 Months Ended
Commitment and Contingencies - Narrative (Details)	Mar. 31, 2017 USD ($)	Dec. 31, 2020 USD ($) vote	Dec. 31, 2019 USD ($)	Aug. 31, 2019 ft²	Jul. 31, 2019 ft²
Lessee, Lease, Description [Line Items]
Number of operating leases \| vote		1
Restricted cash		$ 115,000	$ 115,000
Number of renewal options \| vote		0
Short-term expenses		$ 36,290	1,544
Lexington Lease
Lessee, Lease, Description [Line Items]
Area of rental space (sqft) \| ft²				10,417	10,417
Restricted cash		100,000	$ 100,000
Lexington Lease \| Loans Payable
Lessee, Lease, Description [Line Items]
Loan from landlord	$ 200,000
Interest rate	8.00%
Repayments related to loan		$ 65,000
Lexington Lease \| Loans Payable \| Interest Only
Lessee, Lease, Description [Line Items]
Debt instrument, term	18 months
Lexington Lease \| Loans Payable \| Principal and Interest
Lessee, Lease, Description [Line Items]
Debt instrument, term	3 years 6 months

Commitment and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease cost
Operating lease cost	$ 468	$ 278
Total lease cost	468	278
Other information
Operating lease payments	$ 468	$ 278
Remaining lease term	1 year 10 months 24 days	2 years 10 months 24 days
Discount rate	8.02%	8.02%

Commitment and Contingencies - Maturity of Lease Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
MATURITY OF LEASE LIABILITY
2021	$ 482
2022	497
Total lease payments	979
Less: imputed interest	(80)
Total operating lease liabilities	899
Included in the consolidated balance sheet:
Current portion of lease liabilities	423	$ 376
Lease liabilities	476	$ 899
Total operating lease liabilities	$ 899

Commitment and Contingencies - Future Payments Under Loan Obligation (Details) - Lexington Lease - Loans Payable $ in Thousands	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
2021	$ 65
2022	65
Total payments	$ 130

Revenue from Contracts with Customers (Details) - USD ($)		12 Months Ended
	Dec. 14, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit		$ (65,011,000)	$ (19,650,000)
Research collaboration revenue		$ 0	10,000,000
Deferred revenue			$ 0
License Agreement \| Novo Nordisk A/S
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
License agreement proceeds received				$ 16,000,000.0
Annual collaboration budget funding	$ 2,000,000.0
Cumulative proceeds received from collaboration budget funding				$ 4,000,000.0
Difference between Revenue Guidance in Effect before and after Topic 606 \| Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit					$ 0

Subsequent Events (Details) - Subsequent Event $ in Thousands	Mar. 25, 2021 USD ($) ft²
Subsequent Event [Line Items]
Area of rental space (sqft) \| ft²	2,550
License agreement, monthly payments \| $	$ 14

Label	Element	Value
Restricted Cash	us-gaap_RestrictedCash	$ 115,000
Restricted Cash	us-gaap_RestrictedCash	$ 115,000